Superconducting circuits are one of the leading technologies proposed for quantum computing and cryptography applications that are expected to provide significant enhancements to national security applications where communication signal integrity or computing power are needed. They are operated at temperatures <100 kelvin. Efforts on fabrication of superconducting devices have mostly been confined to university or government research labs, with little published on the mass producing of superconducting devices. Therefore, many of the methods used to fabricate superconducting devices in these laboratories utilize processes or equipment incapable of rapid, consistent fabrication. Furthermore, the need for low temperature processing currently presents one of the more significant barriers to mass production of superconducting devices.
One of the common devices employed in superconducting circuits is a Josephson junction (JJ). Today's typical Josephson junctions (JJs) are formed using a self-aligned anodization process which uses a highly corrosive electrochemical bath to form a protective thick passivation layer around the JJ in the form of a large ring. This thick ring of oxidized superconducting material forms the insulation between the active part of the JJ and the top electrode wiring. Furthermore, the use of legacy processing techniques to form a JJ result in large topography problems and therefore problems with yield and reliability of the JJ. The use of anodization process results in a relatively large JJ area due to the need to mask and etch off the blanket anodization layer away from the JJ ring. Both of these processes lead to a minimum size of JJ of the order of 1 um diameter which limits the density and functionality of an integrated chip.